1. Field of the Invention
The present invention relates to a drive signal output circuit which outputs a drive signal to a load such as a motor and a multi-chip package including the drive signal output circuit.
2. Description of the Related Art
In the related art, an H bridge circuit is used in a drive circuit for a motor or the like. In the H bridge, two series connections each having a p-type transistor and an n-type transistor are placed between a power supply line and a ground line, and intermediate points of the series connections are set as a pair of outputs.
In the H bridge, a load such as a coil is connected to the pair of outputs, and a direction of current to the load is controlled by ON and OFF states of a transistor. As the control signal of each transistor, a sine wave is used, or a simple H signal and a simple L signal are also used. In the latter case, three states are generated, one indicating a current to the load in the forward direction, one indicating a backward direction, and one indicating an OFF state.
For example, in a case of a stepping motor, two coils are used, and two H bridges are used for driving the coils. A rotor position is determined based on the state of the current supplied to the two coils. Because of this, it is possible to rotate the rotor in the forward or backward direction by a desired amount by sequentially changing the state of the current supplied to the two coils in a particular order.
Normally, a signal for driving the H bridge is supplied from outside. Therefore, a circuit which drives the transistor of the H bridge based on the signal supplied from the outside is required. The driving of the load such as the stepping motor, on the other hand, is not necessarily in one mode. It is not efficient to prepare a drive signal output circuit for each load and for each of various modes.